Therefore, a wise general will strive to feed off the enemy.
One bushel of the enemy's provisions is worth twenty of our own, one picul of fodder is worth twenty of our own.

The problem with brakes is that the driver makes a frontal assault on his vehicle's inertia, destroying
it by converting it to heat via the brake pad. Why not use that energy to accomplish your end? Since the real point of an emergency brake is to avoid an obstacle I propose a solution similar to the dragged spikes etc which have been offered in this category, but less hard on the car, road, and driver.

Fire a harpoon into the ground just to the left of the car, attached by a chain to the frame. The car will swing in a tight U around the harpoon When pointing 180 degrees the opposite way, the chain releases. You continue driving along, but now in the opposite lane, away from the obstacle at a substantial fraction of your initial velocity. You have used your enemies' resources to further your end.

Batman had a similar device for going around sharp corners - a grappel which hung onto lamp posts. It was in Batman II I think - but I cant find a link. This strategy I think would be dangerous for passers by and overly reliant on well built lampposts.

This device would be problematic in countries where people routinely drive on the left - deployment of the sun-tsu brake would result in the car hopping the curb, entering buildings etc. Hopefully news reports detailing the benefits of the Sun-Tsu would cause political pressures to switch over and drive on the right.

I'm relieved your back after the fun I had at your expense last we met. Ah, but it was just in fun. Okay?
This idea is classic Bakery material. Whether or not it gets roasted I don't know that yet. You deserve a croissant for giving me a good laugh here anyway.

A harpoon large enough to turn a car travelling at high velocity would have to make quite a destructive impact in the road. I fear the department of roads and transport may have something to say about this.

Maybe there could be a receptacle tracking built into the side of the road in order to catch hold of the standard-shaped harpoon so that the roads would be safe. This would allow for a design of harpoon that can be retracted back to the car and reused.

Its a really fine idea. Very green, energy saving. But I do have a worry about the chain release. If it doesnt, you and your car will turned into a gigantic tether-ball, whirling around at an ever more feverish pace until the chain is completely wrapped around the post, then the sudden neck snapping reversal, the vertebrae separation, the. . .well, as I say, its a worry.

Nick: other cars are not your enemy, your momentum is. Probably I should have called this the Aikido brake. As regards the tetherball possibility, early tests done by me this week (eg: very rapid left turns) have resulted in the accumulation of all my car stuff on the right side of the car, but not me - the shoulder belt holds you in place very nicely.

I like the harpoon receptacle idea. However, to compensate for road damage caused by the harpoon, one could place in them some gold or other valuable material. This would in effect tax harpoon users, since they would need to buy a new harpoon, and city covernments could harvest used harpoons from the road and sell them to cover road repair costs.